This invention pertains to generators including alternators which must operate over a wide range of temperatures, such as aircraft generators, and with means providing for stator retention in fixed position throughout the operating temperature range of the generator.
Aircraft generators must operate over a wide range of temperatures. Generators are presently being designed and built with spray oil cooling to operate from approximately -65.degree. F. to 355.degree. F. A common construction of the generator has the stator comprised of a winding about an iron core inserted into the bore of a housing and in order to save weight the housing is frequently a magnesium or aluminum casting. It is a requirement that the stator be accurately positioned within the housing, both radially and axially throughout the operating temperature range of the generator. Movement of the stator relative to the housing during operation could cause an electrical failure. One common method used to position stators is to provide an interference fit between the outside surface of the stator and the inside surface of the housing.
Due to the relatively high thermal expansion rates of magnesium or aluminum, as compared to the iron used for the stator core, problems are often encountered in retaining the stator within the housing throughout the complete operating temperature range which, in the example given above, could be 420.degree. F. For example, a magnesium housing can only undergo approximately a 250.degree. F. temperature range without either yielding at the low temperature or permitting the stator to loosen at the higher temperatures. At present in order to extend the temperature range capabilities beyond 250.degree. F., a number of screws are positioned radially through the housing of the generator and in an oil spray cooled generator these screws must be sealed to prevent oil from leaking out of the generator.